Code 24, Vehicle Speed Sensor Circuit: Notes

ECM supplies a B+ signal to Vehicle Speed Sensor (VSS). While vehicle is moving, a reed switch inside VSS will open and close, toggling B+ signal high and low. ECM then converts this toggled high/low voltage into a vehicle speed that is displayed as MPH/KPH.

Code 24 will set if a constant voltage signal (high or low) is not detected at ECM for at least 4 seconds, with engine running and vehicle moving.

1. Checks to see if problem is intermittent.
2. If VSS is not receiving the 12 volts from the ECM, Code 24 will set. This step checks for an open in the Yellow/Green wire or for a faulty ECM.
3. This checks for a poor ground connection, an open in the Black/Blue wire or for a faulty VSS.